Image reading apparatus, control method, and control program

Abstract

An image reading apparatus, a control method, and a control program accurately determining a position of a foreign object are provided. The image reading apparatus includes an image capturing device, provided in a first unit or a second unit, for capturing a first image and a second image, a reference member provided in the first unit or the second unit, a driving device for moving the second unit, a foreign object determining module for determining whether or not a foreign object appears in the first image, and a position determining module for determining whether the foreign object exists on the image capturing device side or on the reference member side, based on an absolute value of a difference between a gradation value in a region where the foreign object appears within the first image and a gradation value in a region corresponding to the region where the foreign object appears, within the second image when the foreign object appears in the first image, wherein the first image is an image of the reference member captured when the second unit is provided at one of the first position or the second position, and the second image is an image of the reference member captured when the second unit is provided at the other of the first position or the second position.

The invention claimed is: 
     
       1. An image reading apparatus comprising:
 a first unit fixed to the image reading apparatus; 
 a second unit movable between a first position facing the first unit and a second position facing the first unit and more separated from the first unit than the first position; 
 an image capturing device, provided in one of the first unit or the second unit, for capturing a first image and a second image; 
 a reference member provided in another one of the first unit or the second unit; 
 a driving device for moving the second unit between the first position and the second position; and 
 a processor configured to
 determine whether or not a foreign object appears in the first image, and 
 determine whether the foreign object exists on a side of the image capturing device or on a side of the reference member, based on an absolute value of a difference between a gradation value in a region where the foreign object appears within the first image, and a gradation value in a region where the foreign object appears within the second image when the foreign object appears in the first image, 
 
 wherein the first image is an image of the reference member captured when the second unit is at one of the first position or the second position, and the second image is an image of the reference member captured when the second unit is provided at another one of the first position or the second position. 
 
     
     
       2. The image reading apparatus according to  claim 1 , wherein the processor determines that the foreign object exists on the side of the image capturing device when the absolute value of the difference is smaller than a predetermined threshold, and the processor determines that the foreign object exists on the side of the reference member when the absolute value of the difference is equal to or larger than the predetermined threshold. 
     
     
       3. The image reading apparatus according to  claim 1 , wherein
 the image capturing device further captures a reference image for correcting a document image that is a captured image of a document, and 
 the processor does not correct the reference image when the foreign object exists on the side of the image capturing device, and corrects the reference image when the foreign object exists on the side of the reference member. 
 
     
     
       4. The image reading apparatus according  claim 1 , wherein the second unit is movable by a document transferred to the image reading apparatus, even when the driving device is inactive. 
     
     
       5. The image reading apparatus according to  claim 1 , further comprising a light source for emitting light to the reference member,
 wherein the image capturing device further captures a third image of the reference member captured under illumination of the light with a first light quantity from the light source, and a fourth image of the reference member captured under illumination of the light with a second light quantity from the light source, the second light quantity being different from the first light quantity, and 
 the processor determines whether the foreign object exists on the side of the image capturing device or on the side of the reference member, based on an absolute value of a difference between a gradation value in the region where the foreign object appears within the third image, and a gradation value in a region where the foreign object appears within the fourth image. 
 
     
     
       6. The image reading apparatus according to  claim 5 , wherein the processor determines a position where the foreign object appears, based on the first image and the second image, at a time of staring up the image capturing device, and determines a position where the foreign object appears, based on the third image and the fourth image, at a time of document transfer. 
     
     
       7. A control method of an image reading apparatus including a first unit fixed to the image reading apparatus, a second unit movable between a first position facing the first unit and a second position facing the first unit and more separated from the first unit than the first position, an image capturing device, provided in one of the first unit or the second unit for capturing a first image and a second image, a reference member provided in another one of the first unit or the second unit, and a driving device for moving the second unit between the first position and the second position, the method comprising:
 determining whether or not a foreign object appears in the first image; and 
 determining whether the foreign object exists on a side of the image capturing device or on a side of the reference member, based on an absolute value of a difference between a gradation value in a region where the foreign object appears within the first image, and a gradation value in a region where the foreign object appears within the second image when the foreign object appears in the first image, 
 wherein the first image is an image of the reference member captured when the second unit is at one of the first position or the second position, and the second image is an image of the reference member captured when the second unit is provided at another one of the first position or the second position. 
 
     
     
       8. A computer-readable, non-transitory medium storing a computer program, wherein the computer program causes an image reading apparatus including a first unit fixed to the image reading apparatus, a second unit movable between a first position facing the first unit and a second position facing the first unit and more separated from the first unit than the first position, an image capturing device, provided in one of the first unit or the second unit for capturing a first image and a second image, a reference member provided in the other of the first unit or the second unit, and a driving device for moving the second unit between the first position and the second position, to execute a process, the process comprising:
 determining whether or not a foreign object appears in the first image; and 
 determining whether the foreign object exists on a side of the image capturing device or on a side of the reference member, based on an absolute value of a difference between a gradation value in a region where the foreign object appears within the first image, and a gradation value in a region where the foreign object appears within the second image when the foreign object appears in the first image, 
 wherein the first image is an image of the reference member captured when the second unit is at one of the first position or the second position, and the second image is an image of the reference member captured when the second unit is provided at another one of the first position or the second position.